As well known in the art, dynamoelectric machines are provided with a rotatable member or assembly, generally referred to as a rotor, a stationary member, generally referred to as a stator, in which the rotatable member is received, and structural components, such as opposite end frames or shields, which are secured to the stationary member and rotatably support or journal the rotatable member.
In dynamoelectric machines of the type just described, it is most important that the rotor and stator be mounted or assembled during manufacture in proper radial and axial alignment, and that such be done expeditiously and inexpensively. Improper radial alignment results in undesirable eccentricity in an annular air gap between the rotor and magnetic core while improper axial alignment produces undesirable excessive axial rotor thrust. It is also important that the end frames be properly aligned with the stator and rotor to ensure longevity for the bearing means of the end frames.
In the past, several different methods of assembling dynamoelectric machines with the rotor thereof properly positioned within the stator and with the end frames properly mounted with respect to the stator and rotor having the bearing means thereof for supporting engagement with the rotor mutually aligned along a common axis. For example, stators have been connected to end frames by through-bolts; however, proper radial alignment here is achieved principally through close tolerance fits between the dynamoelectric components. With such methods, the tighter the tolerances are held, the more accurate the resulting alignment; however, one of the disadvantageous or undesirable features of such method is that close tolerances not only are costly to effect during manufacture but also impede assembly.
Another method of mounting components of a dynamoelectric machine was one in which an oversized dummy rotor was used to assemble and align the dynamoelectric machine components with an actual rotor being subsequently substituted after alignment between rotor and stator was achieved. Such use of dummy rotors, however, was limited to "unit bearing" type machines, that is dynamoelectric machines in which the rotor is supported at one end only. A disadvantageous or undesirable feature of this method was that it was unavailable for use with the great majority of dynamoelectric machines wherein the rotor is rotatably supported at both ends of its shaft in opposite end frames.
U.S. Pat. No. 3,165,816 disclosed a different approach to assembling dynamoelectric machines. Shims were arranged in the air gap between rotor and stator, and opposite end frames were disposed adjacent the end faces of the stator in journaling engagement with the rotor. The stator and end frames were then bonded together with an adhesive bonding material, such as a thermosetting resin or the like, thereby securing the stator and end frames together upon curing of the adhesive.
U.S. Pat. No. 3,705,994 disclosed a method by which the end portions of a set of beams attached to a stator of a dynamoelectric machine were welded to a pair of opposite end frames; however, one of the disadvantageous or undesirable features thereof was that the welds establish stresses upon cooling which tend to distort the preferred alignment of the dynamoelectric machine components, as is well known in the art.